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Estimating the accuracy of thermography of disconnector contacts in the field
KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
2008 (English)Report (Other academic)
Abstract [en]

This report summarises the results from an investigation into the accuracy of condition assessment of electrical contacts via thermography measurements in the field. The investigation was carried out in Ludvika, Sweden at the Swedish Transmission Research Institute (STRI) outdoor test site during the autumn of 2007. The investigation was performed as a part of the PhD project Modelling of power equipment reliability with special reference to the impact of maintenance carried out at the RCAM research group at the KTH School of Electrical Engineering.

Two naturally aged disconnector poles of the make ABB NSA 400/3150 was loaded up to their nominal load in three stages and the contact temperature rises were measured both using thermography and thermocouples attached to the contacts. The thermography measurements were carried out by am experienced technician from Vattenfall Service. After the first set of measurements some contacts were subjected to standard maintenance and the measurements were repeated.

The investigation resulted in statistical distribution for the errors related to the estimation of contact temperature rise at nominal load based on thermography measurements. These error distributions were used to simulate the accuracy of the estimations. Furthermore the investigation resulted in two linear regression models of the relationship between contact resistance and temperature rise as well as the effect of maintenance on contact temperature rise.

A conclusion from the measurements was that statistical models should be used to estimate the effect of maintenance on the contact condition as well as estimating the contact condition from resistance measurements.

Place, publisher, year, edition, pages
2008. , 26 p.
Series
Trita-EE, ISSN 1653-5146 ; 2008:010
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:kth:diva-8182OAI: oai:DiVA.org:kth-8182DiVA: diva2:13435
Note
QC 20100823Available from: 2008-04-03 Created: 2008-04-03 Last updated: 2010-08-23Bibliographically approved
In thesis
1. On reliability and maintenance modelling of ageing equipment in electric power systems
Open this publication in new window or tab >>On reliability and maintenance modelling of ageing equipment in electric power systems
2008 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

Maintenance optimisation is essential to achieve cost-efficiency, availability and reliability of supply in electric power systems. The process of maintenance optimisation requires information about the costs of preventive and corrective maintenance, as well as the costs of failures borne by both electricity suppliers and customers. To calculate expected costs, information is needed about equipment reliability characteristics and the way in which maintenance affects equipment reliability. The aim of this Ph.D. work has been to develop equipment reliability models taking the effect of maintenance into account.

The research has focussed on the interrelated areas of condition estimation, reliability modelling and maintenance modelling, which have been investigated in a number of case studies. In the area of condition estimation two methods to quantitatively estimate the condition of disconnector contacts have been developed, which utilise results from infrared thermography inspections and contact resistance measurements. The accuracy of these methods were investigated in two case studies. Reliability models have been developed and implemented for SF6 circuit-breakers, disconnector contacts and XLPE cables in three separate case studies. These models were formulated using both empirical and physical modelling approaches. To improve confidence in such models a Bayesian statistical method incorporating information from the equipment design process was also developed. This method was illustrated in a case study of SF6 circuit-breaker operating rods. Methods for quantifying the effect of maintenance on equipment condition and reliability have been investigated in case studies on disconnector contacts and SF6 circuit-breakers. The input required by these methods are condition measurements and historical failure and maintenance data, respectively.

This research has demonstrated that the effect of maintenance on power system equipment may be quantified using available data. However, realising the full potential of these methods requires the gathering and utilisation of failure and maintenance data as well as condition measurements to be improved.

Place, publisher, year, edition, pages
Stockholm: KTH, 2008. ix, 55 p.
Series
Trita-EE, ISSN 1653-5146 ; 2008:016
Keyword
Reliability, maintenance, electric power systems, circuit breaker, disconnector, thermography
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-4688 (URN)978-91-628-7465-0 (ISBN)
Public defence
2008-04-25, F3, Lindstedtvägen 26, Stockholm, 13:15
Opponent
Supervisors
Note
QC 20100823Available from: 2008-04-03 Created: 2008-04-03 Last updated: 2010-08-23Bibliographically approved

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